[vorbis] what is floor?

[Giuliano Pochini]

On Fri, 3 Oct 2003, Vincent wrote:

> hello,
>
> can someone please explain me how "floors" work.
> how are they normalized?
> i got this from the xiph.org web site, and i don't understand it very well:
>
> "Vorbis I stream first generates from input audio a spectral 'floor'
> function that serves as an MDCT-domain whitening filter. This floor is meant
> to represent the rough envelope of the frequency spectrum. This floor is
> subtracted from the log frequency spectrum, effectively normalizing the
> spectrum by frequency"
>
> can someone explain me ?

I may be wrong, but the floor is a smoothed version of the frequency
spectrum. When you subtract it from the actual spectrum you get a
quite flat spectrum, a sort of white noise. It still contains a lot
of information that has to be saved in order to be able to eventually
recreate the original sound.

<p>
--
Giuliano.
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